1. Field of the Invention
This invention relates to a system for testing imaging devices and more specifically to a system, using correlation techniques for determining defects in imaging devices.
2. Description of Related Art
Because artifacts in an image distort the image, it has become necessary to identify the imaging devices which produce artifacts during their manufacturing, calibration, or field use. These artifacts may be difficult to identify visually and more difficult to identify visually when superimposed upon an image. If the artifacts are not corrected in images, they my be perceived as actual structures in the image. This may be the case in medical imaging where artifacts in the image might be perceived as clinical features in a patient, leading to misdiagnosis. These imaging devices may be medical imaging systems such as Gamma Cameras used in imaging radioactive tracers introduced into a patient's body, X-ray imaging devices, and magnetic resonance (MR)imaging systems.
Prior art methods of detecting defects in Gamma Cameras, for example, are determined by an operator visually examining artifacts in an image produced by a Gamma Camera stimulated by a constant intensity gamma radiation source. This results in a very subjective test that varies greatly from camera to camera.
In Gamma cameras, for example, artifacts may appear as:
1) tubular or hexagonal "hex" patterns showing a distinct evenly spaced dark and light patterns; PA0 2) secondary tube or "hex" patterns, which are differently sized evenly spaced dark and light circular or hexagonal patterns; PA0 3) tramlines, which appear as lines through the image; PA0 4) non-functional tubes, which appear as one or more dark or light regions having little relation to each other PA0 5) bright or dark regions near the edges of the image; and 6) general blotches throughout the image.
Currently, there is a need for a reliable and accurate system to detect and quantify artifacts indicating defects in imaging devices, and adjust the devices to reduce or eliminate the artifacts.